Federal agents sneaked a cellphone into Men's Central Jail as part of their investigation of misconduct, sources say.

Federal authorities are investigating allegations of inmate beatings and other misconduct by deputies in Los Angeles County jails, with FBI agents going so far as to sneak a cellphone to an inmate to get reports from inside, according to law enforcement sources.

The inquiries include allegations that deputies broke an inmate's jaw and other facial bones and beat another man for two minutes while he was unconscious.

Their investigation created a flap recently when Los Angeles County Sheriff's Department brass discovered that an inmate inside Men's Central Jail was an FBI informant equipped with a cellphone he was believed to be using to communicate with agents on the outside.

Sheriff Lee Baca, who had not been notified by the feds of the plant inside his jail, is expected to meet with U.S. Atty. André Birotte Jr. soon to discuss the phone incident and the growing tensions between the two law enforcement agencies.

The jail probes mark the third federal investigation of the Sheriff's Department in recent months. Last month, the U.S. Department of Justice's civil rights division announced a wide scale "pattern and practice" investigation into allegations that deputies in the Antelope Valley discriminated against minority residents who receive government housing assistance. Also last month, The Times reported that a Sheriff's Department captain had been put on leave after federal agents suspected hearing her voice on a wiretap of a suspected Compton drug ring.

Federal officials declined to discuss details of their probes in the largest jail system in the nation. The lockups are already under federal court oversight for overcrowding and poor conditions and are due to absorb thousands of offenders who previously would have been housed in state prisons.

The jails have been plagued with problems over the last decade, including inmate riots, killings, antiquated facilities, huge settlements and even the formation of a gang-like deputies clique. Inmate accusations of beatings are common within the many facilities that make up the department's jail system, but most are unsubstantiated.

After sheriff's officials discovered the FBI cellphone, the Sheriff's Department placed one deputy, Gilbert Michel, on leave. He was being investigated by the department on suspicion of allowing a contraband cellphone behind bars, according to sources who requested anonymity because they were not authorized to discuss the investigation. Shortly thereafter, Michel resigned, a source said. Michel, 38, could not be reached for comment.

Sheriff's spokesman Steve Whitmore called the federal scrutiny of the jails unnecessary, saying the department already thoroughly evaluates allegations of deputy misconduct. Last year, he said, more than a dozen deputies were fired for bad behavior in the lockups.

"There is nothing that's being hidden," Whitmore said. "Inmates that complain and say they've been brutalized ... most of them turn out to be not what the inmate said occurred. The ones that turn out to be valid are dealt with appropriately."

Whitmore said sneaking a phone into the jails is a serious breach of security that could put inmates, deputies and the public at risk. He said he did not know whether the feds had any safeguards in place to monitor the phone. Federal authorities declined to discuss the matter. The department has launched an investigation into the incident, including the FBI's role in "colluding with an inmate" to get a cellphone behind bars, he said.

Whitmore declined to discuss any role the deputy had in getting the cellphone into the jail. "We're going to get to the bottom of it," Whitmore said.

Federal authorities have previously acknowledged at least one current criminal investigation into the allegation of a beating of an inmate by two deputies at Twin Towers jail, an encounter witnessed by an American Civil Liberties Union monitor.

Esther Lim, the ACLU monitor, said she happened on two deputies punching and using a stun gun on the limp body of an inmate for two minutes.

Lim was interviewed by the FBI in January. At the time, agents asked her only about the specific event. She has been interviewed again, this time about broader deputy-inmate interactions, according to her attorney, Michael Proctor.

After The Times wrote about the beating Lim described, a federal prosecutor subpoenaed the newspaper for information that would identify two anonymous commenters on The Times' website who claimed they came across incidents of deputy brutality, allegations unrelated to the Lim incident.

One commenter described "brutal beatings of prisoners on a daily basis" at the jail ward of the Los Angeles County-USC Hospital. The other, a self-described emergency medical services provider, recalled frequently being called to jail facilities to "pick up the sheriff's assault victims."